“…In this paper, we focus our discussions on two effects: domain wall dynamics and magnetization instability. Recently, both topics have received considerably interests in experiments [1,2,3,4,5,6,7,8,9,10,11] and in theories [12,13,14,15,16,17,18,19]. It is shown that the current is able to displace magnetic domain walls in a spin valve [3], in a constricted nanowire [4], in U-shaped (or L-shaped) nanowires [5,6], in a ring structure [7] and in zigzag wires [8].…”